Obliteration of bacterial growth and biofilm through ROS generation by facilely synthesized green silver nanoparticles

Mangifera indica inflorescence aqueous extract was utilized for production of green AgNPs. Synthesized AgNPs were characterized by UV-vis spectrophotometry, XRD, TEM, FESEM and particles size analyzer. AgNPs showed minimum inhibitory concentrations (MICs) of 8 μg ml-1 and 16 μg ml-1 for Gram negative (K. pneumoniae, P. aeruginosa and E. coli) and Gram positive (S. mutans and S. aureus) strains, respectively which was relatively quite low compared to chemically synthesized silver nanoparticles. AgNPs inhibited 80% and 75% biofilms of E. coli and S. mutans respectively as observed quantitatively by crystal violet assay. Qualitative biofilm inhibition was observed using SEM and CLSM. AgNPs adsorbed catheter also resisted the growth of biofilm on its surface displaying its possible future applications. AgNPs interaction with bacteria lead to bacterial membrane damage as observed by SEM and TEM. The membrane damage was confirmed by detecting leakage of proteins and reducing sugars from treated bacterial cells. AgNPs generated ROS on interaction with bacterial cells and this ROS production can be one of the possible reasons for their action. AgNPs exhibited no toxic effect on the cell viability of HeLa cell line.